With the refined service operations of authentication, authorization and accounting (AAA), operators may propose various new requirements, such as one card for multiple applications, to enhance the user satisfaction and competitiveness. One card for multiple applications means that a user can enable multiple users to use the card at the same time. This is very convenient for some specific user groups. One card for multiple applications is applicable to postpaid users. Because it is a postpaid service, no overdraft case may occur. No matter how many users are using a card, the account is rated and charged based on the actual traffic. For a prepaid account, there is a balance limit. The AAA server should budget the available traffic and send it to the network access server (NAS). After the available traffic is used up, the NAS stops providing services to the user.
FIG. 1 shows the Internet access process of a prepaid account over the standard Radius protocol.
Step 101: A user performs PPP/PPOE/802.1X dialing on a terminal (TM).
Step 102: After receiving the dialing request, the NAS sends a Radius Access-Request to the AAA server.
Step 103 to step 104: After receiving the Radius Access-Request, the AAA server authenticates the user. If the authentication fails, the AAA server sends an Access-Reject message; if the authentication succeeds, the AAA server calculates the available traffic of the user based on the balance of the account. If the available traffic is greater than 0, the AAA server returns a Radius Access-Accept message to the NAS, and the available traffic is the actual calculation result. If the available traffic is equal to 0, the AAA server returns an Access-Reject message, and the available traffic is delivered through the Access-Accept message;
Step 105: After receiving the Access-Accept message, the NAS notifies the TM of successful dialing and opens the Internet access authority for the user. The authentication process ends.
Step 106 to step 107: Upon successful authentication, the NAS sends an Accounting-Request-Start message to the AAA server, and the AAA server returns an accounting start response message directly.
Step 108 to step 110: The NAS sends an Accounting-Request-Interim message to the AAA server periodically, and the AAA server settles fees, deducts fees and generates bills based on the user's actual traffic and the accounting policy preset on the AAA server, and returns an interim accounting response message.
Step 111 to step 115: If the user gets offline actively or the available traffic delivered by the AAA server is used up, the NAS sends an Accounting-Request-End message to the AAA server; the AAA server settles fees, deducts fees and generates bills based on the user's actual traffic and the accounting policy preset on the AAA server, and returns an accounting end response message to the NAS; the NAS notifies the TM of getting offline successfully. The Internet access process of the user ends.
It is evident that the available traffic is calculated based on the balance of an account. The preceding process supports the standard Radius protocol, where the available traffic is delivered with the Access-Accept message and remains unchanged. During the invention, the inventor discovers the following problem: If multiple users use a same card and each user gets online by using the preceding process, the AAA server may calculate the available traffic based on the balance of the account of each user. In this case, if each user gets offline only when the available traffic is used up, the fee is not enough and overdraft may occur. Thus, when the standard Radius protocol is used, a prepaid account cannot be used by multiple users.